U.S. patent number 6,248,109 [Application Number 09/509,423] was granted by the patent office on 2001-06-19 for implant for interconnecting two bone fragments.
This patent grant is currently assigned to Waldemar Link (GmbH & Co.). Invention is credited to Rudolf Stoffella.
United States Patent |
6,248,109 |
Stoffella |
June 19, 2001 |
Implant for interconnecting two bone fragments
Abstract
An implant for fixing two bone fragments to each other comprises
a clasp (4) with two arms (7) which are connected to each other at
one of their ends and in this area form an eyelet with an opening
(8) for passage of a screw (6) which can be screwed into one (3) of
the two bone fragments. The free ends of the two arms (7) are
introduced into the medullary cavity of the other bone fragment (2)
and are anchored therein by spreading apart. To improve the
anchoring of the clasp (4) on the bone fragment (3), a shim part
(5) is arranged between the clasp (4) and the head (9) of the screw
(6), which shim part (5) has a recess for receiving the clasp (4)
and is provided with spikes (11) which penetrate into the bone
fragment (3).
Inventors: |
Stoffella; Rudolf (Modling,
AT) |
Assignee: |
Waldemar Link (GmbH & Co.)
(Hamburg, DE)
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Family
ID: |
3511280 |
Appl.
No.: |
09/509,423 |
Filed: |
March 28, 2000 |
PCT
Filed: |
July 02, 1999 |
PCT No.: |
PCT/EP99/04630 |
371
Date: |
March 28, 2000 |
102(e)
Date: |
March 28, 2000 |
PCT
Pub. No.: |
WO00/06036 |
PCT
Pub. Date: |
February 10, 2000 |
Foreign Application Priority Data
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Jul 30, 1998 [AT] |
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1317/98 |
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Current U.S.
Class: |
606/75; 606/327;
606/62 |
Current CPC
Class: |
A61B
17/68 (20130101); A61B 17/809 (20130101); A61B
2017/565 (20130101) |
Current International
Class: |
A61B
17/68 (20060101); A61B 017/86 () |
Field of
Search: |
;606/60,62,67,68,72,73,75 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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000937 U |
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Aug 1996 |
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AT |
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0288229 |
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Oct 1988 |
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EP |
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Primary Examiner: Reip; David O.
Attorney, Agent or Firm: Morrison & Foerster LLP
Claims
What is claimed is:
1. Implant for fixing two bone fragments (2, 3) to each other, in
particular for fixing an axially corrected capitulum of a
metatarsal bone, e.g. hallux valgus, which implant comprises a
clasp (4) with two arms (7) which are connected to each other at
one of their ends and in this area form an eyelet with an opening
(8) for passage of a screw (6) which can be screwed into one (3) of
the two bone fragments, and which, with their other, free ends, can
be introduced into the other bone fragment (2), wherein a shim part
(5), through which the screw (6) is passed, is arranged between the
clasp eyelet and the screw head (9), which shim part (5) is
provided with projections (11) which can be anchored in the bone
fragment (3).
2. Implant according to claim 1, wherein the shim part (5) is in
the shape of a circular annulus and the projections are designed as
spikes (11) protruding essentially at right angles from the annular
plane.
3. Implant according to claim 2, wherein the shim part has a recess
receiving the clasp in the area of the eyelet and a lateral slot
permitting passage of the arms of the clasp.
4. Implant according to claim 2, wherein the shim part comprises at
least three projections.
5. Implant according to claim 2, wherein the shim part is made of a
tissue-compatible material.
6. Implant according to claim 1, wherein the shim part (5) has a
recess (12) receiving the clasp (4) in the area of the eyelet, and
a lateral slot (13) for passage of the arms (7) of the clasp
(4).
7. Implant according to claim 6, wherein the shim part comprises at
least three projections.
8. Implant according to claim 6, wherein the shim part is made of a
tissue-compatible material.
9. Implant according to claim 1, wherein the shim part (5) has at
least three projections (11).
10. Implant according to claim 9, wherein the shim part is made of
a tissue-compatible material.
11. Implant according to one of claim 1, wherein the shim part (5)
is made of a tissue-compatible material.
Description
FIELD OF THE INVENTION
The invention relates to an implant for fixing two bone fragments
to each other, in particular for fixing an axially corrected
capitulum of a metatarsal bone, e.g. hallux valgus.
BACKGROUND OF THE INVENTION
Osteotomies for treating hallux valgus have already been known for
decades and have the object of functionally reconstructing the axis
of the 1st metatarsal. It is necessary in this context, after the
osteotomy, to fix the two bone fragments in their corrected
position in order to prevent mobility between the fragments and to
permit reliable osseous union without dislocation.
To fix the osteotomy, it is already known to use plates which are
secured to the cortical bone by means of a number of screws in
order to prevent the bone fragments from buckling. A considerable
surgical outlay is required for this.
Bone clamps are also known for fixing the osteoLomy, but their use
involves the risk of splintering of the bone.
AT 937 U has disclosed an implant for fixing two bone fragments to
each other, in particular for treating an axial deviation of a
metatarsal bone, e.g. hallux valgus, which implant comprises a
clasp with two arms which are connected to each other at one of
their ends and in this area delimit an opening for passage of a
screw which can be screwed into one of the two bone fragments and
which, with their other, free ends, can be introduced into the
medullary cavity of the other bone fragment and can spread apart.
After osteotomy has been performed, the clasp is introduced
proximally into the medullary cavity of one bone fragment via the
free ends of the two arms and spreads apart in this medullary
cavity, after which the clasp is anchored on the other bone
fragment by means of the screw guided through the opening.
As a result of the spreading force and the frictional fit of the
clasp arms, and as a result of the intermittent compression arising
upon functional loading, the intramedullary part of this known
implant has a high degree of stability. By contrast, however, the
extramedullary part is anchored in the bone via only one screw,
whereas a two-point bearing is required on account of the torque
which increasingly occurs as the compression of the screw anchoring
between implant and metatarsal head decreases.
SUMMARY OF THE INVENTION
The object of the present invention is to improve and stabilize the
fixing of this known implant to the one of the two bone fragments
connected to the implant via the screw, without in so doing having
to modify the surgical procedure. To achieve this object, the
invention proposes that a shim part, through which the screw is
passed, be arranged between the clasp opening and the screw head,
which shim part has projections which can be anchored in the bone
fragment. These projections provide for fixing of the clasp to the
bone fragment in addition to the screw, as a result of which the
stability is considerably improved. The shim part is preferably in
the shape of a circular annulus and has spikes protruding
essentially at right angles from the annular plane, which spikes
penetrate or are pressed into the bone fragment and are thus
securely anchored in the bone fragment.
A preferred embodiment of the implant according to the invention is
characterized in that the shim part has a recess receiving the
clasp with form fit in the area of the opening, and a lateral slot
for passage of the arms of the clasp. This embodiment affords a
form fit between the shim part and the clasp and thereby reliably
prevents the clasp from twisting about the screw axis. The shim
part is pressed onto the bone fragment (or vice versa) by the
screw, preventing a change in the position of the spikes
penetrating into the bone fragment. The invention makes it possible
to connect the two bone fragments to each other in a stable manner
directly without special bone incision.
It is expedient for the shim part to have at least three
projections.
This shim part is preferably made of a tissue-compatible material,
for example stainless steel according to ISO 5832/1.
BRIEF DESCRIPTION OF THE DRAWINGS
An illustrative embodiment of the implant according to the
invention is shown diagrammatically in the drawings. FIG. 1 shows
the use of the implant according to the invention in the
reconstruction of a hallux valgus. FIG. 2 is a plan view of the
clasp forming part of the implant according to the invention, and
FIG. 3 shows a side view of the individual parts of the implant
according to the invention, in an exploded representation. FIG. 4
shows a bottom view of the shim part of the implant according to
the invention, and FIG. 5 shows a section along the line V--V in
FIG. 4.
DETAILED DESCRIPTION OF THE INVENTION
In FIG. 1, a metatarsal bone 1 is represented following osteotomy
and correction, the two bone fragments 2, 3 being fixed by means of
an implant according to the invention. This implant according to
the invention consists of a clasp 4, a shim part 5 and a bone screw
6.
As can be seen in particular from FIG. 2, the clasp 4 has two arms
7 which are connected to each other at one of their ends and there
delimit an eyelet-shaped opening 8. When the bone fragments 2, 3
are being fixed, the free ends of the two arms 7 are introduced
into the medullary cavity of the bone fragment 2 and there take up
their spread-apart position shown in FIG. 2, as a result of which
the clasp 4 is anchored in this medullary cavity. This anchoring is
assisted by an undulating configuration preferably running in the
plane of the arms.
The clasp 4 is then anchored in the bone fragment 3 by means of the
bone screw 6 which is guided through the opening 8.
According to the invention, the shim part 5 is now arranged between
the head 9 of the screw 6 and the clasp 4 in the area of the
opening 8, which shim part 5 is of annular design and has an
opening 10 whose diameter corresponds approximately to that of the
opening 8. This diameter is smaller than the diameter of the head 9
of the screw 6, so that this head 9 bears on the shim part 5.
On the underside the shim part 5 has spikes 11 which, before the
bone screw 6 is screwed into the bone fragment 3, are pressed into
this bone fragment. The shim part 5 is provided with a recess 12
which is designed as an annular groove and which is adapted to the
measurements of the eyelet part of the clasp 4 and receives this
area of the opening 8, and it has a lateral slot 13 through which
the arms 7 of the clasp 4 can emerge. In this way, the shim part 5
is connected to the clasp 4 with a form fit, and relative movement
between the shim part 5 and the clasp 4 is prevented. The shim part
5 is anchored firmly and non-rotatably on the bone fragment 2 by
means of the bone screw 6 and the spikes 11. As a result of the
form-fit connection between the shim part 5 and the eyelet of the
clasp 4, which is maintained between bone surface and screw head by
the clamping of these parts, the clasp 4 is thus also prevented
from moving relative to the bone fragment.
* * * * *